1. Field of the Art
The present invention relates in general to a microwave heating device or apparatus, and more particularly to such heating device for irradiating dielectric or non-conducting material such as food, wood, fibers, and ceramics by means of microwave radiation which is channeled or conducted through a waveguide toward the materials, to thereby heat and dry the materials.
2. Related Art Statement
A microwave heating device or apparatus is known in the art, which includes a microwave oscillator to produce microwave radiation, and a waveguide for channeling or conducting the microwave radiation from the oscillator into a heating room or chamber to irradiate and thereby heat non-conducting or dielectric materials or substances such as food, wood, fibers and ceramics by means of the microwave radiation introduced into the heating chamber. Generally, the materials to be heated are placed on a platform or stand provided in the heating chamber, and the platform with the materials placed thereon is rotated. In the meantime, the heating chamber is formed with an opening to which one end of the waveguide is connected for introducing the microwave radiation into the heating chamber. In such microwave heating devices, a fan or fans (rotary blades) are provided in the heating chamber, so that the microwaves radiated from the end of the waveguide into the heating chamber are irregularly reflected in the chamber so as to obtain uniform distribution of the microwave radiation for even irradiation of the material to be heated.
However, the above-indicated known microwave heating devices suffer some inconveniences which will be described. That is, the fans disposed in the heating chamber for stirring or dispersing the incident microwave radiation will not cause sufficient irregular reflection of the microwave radiation in the heating chamber, i.e., will not permit uniform distribution of the microwaves for even irradiation of the materials to be heated. In other words, the provision of such fans is not satisfactory for even or uniform heating of the material by the microwave radiation. Uneven heating and drying of the material, for example, will result in unveven moisture distribution of the processed article, which is a drawback that requires a solution for quality control of the article.
In the case where the microwave heating device is provided with a material platform which is rotatable, the drive system for rotating the platform is very much complicated, particularly when the microwave heating process is effected in a continuous fashion while the materials to be heated are fed in succession. In this particular case of continuous feeding of the materials, the connection of the material feeding system and the waveguide to a production line makes the heating equipment as a whole considerably large-sized, requiring a relatively large installation space for the equipment. Consequently, the productivity per unit area of the installation space is reduced, while the equipment cost, and operating and maintenance costs of the equipment are increased. Further, the need of a complicated drive system for the rotary material platform leads to reduced surface area on the platform for accommodating the materials. Moreover, there are materials or articles the size or configuration of which does not permit the materials to be rotated by a rotary type platform. Fundamantally, the microwave heating device with a rotary material platform is not applicable to such kinds of materials.